Mixing Covid Vaccine Doses May Raise Side Effects

Mixing Covid-19 vaccine doses — second dose from a different brand than the first — is safe, but may present more frequent mild side-effects such as a headache, chills, or a fever, showed results of a preliminary study published in the Lancet. The study led by University of Oxford researchers, earlier this year, began to investigate the effect of alternate doses of the Oxford-AstraZeneca vaccine and the Pfizer vaccine.

The team examined more than 800 adults aged 50 and over who had received mixed vaccine doses at a four-week interval. When given at a four-week interval, both of the ‘mixed’ schedules (Pfizer-BioNTech followed by Oxford-AstraZeneca, and Oxford-AstraZeneca followed by Pfizer-BioNTech) induced more frequent reactions following the 2nd, ‘boost’ dose than the standard,’non-mixed schedules.